Disc brake

ABSTRACT

A disc brake ( 10 ) comprises a disc ( 12, 14 ), friction material pads ( 26 ) arranged on opposite sides of the disc, and an operating mechanism ( 50, 52 ) operable to bring the pads into contact with the disc so that the pads apply a braking force to the disc. The brake ( 10 ) also comprises a slideway ( 72   a ) on which at least one of the pads ( 26 ) is suported for sliding movement towards or away from the disc ( 12, 14 ). The slideway ( 72   a ) is formed by a guidance member ( 72 ) which defines at least two parallel grooves ( 72   b ) in a surface ( 72   c ) of the guidance member. The grooves ( 72   b ) extend parallel to the direction of the slideway ( 72   a ). The guidance member ( 72 ) is supported by parallel rods ( 70 ) which are received in the grooves ( 72   b ).

BACKGROUND OF THE INVENTION

1. Technical Field

This invention is concerned with a disc brake, eg for the wheel of avehicle.

2. Related Art

In WO 98/25804, there is disclosed a disc brake which comprises twodiscs mounted on the same hub to rotate with the hub about a centralaxis of the hub, and friction material pads arranged on opposite sidesof both discs including two pads between the discs. The discs areslidable axially on the hub and the pads are slidable in a paralleldirection except for one pad which is fixed relative to the hub. Saiddisc brake also comprises an operating mechanism operable to bring thepads into contact with the discs to apply a braking force thereto. Thebrake also comprises a slideway on which at least one of said pads issupported for sliding movement towards or away from the disc. Theslideway comprises a guidance member on which the movable pads areslidably-supported, ie the guidance member provides a slideway on whichpads are supported for movement towards or away from said discs. Theoperating mechanism, which comprises a hydraulically-operated piston andcylinder assembly, the cylinder of which is fixed on a suspension link.The operating mechanism operates to move a first of the pads on theslideway into contact with a first of the discs, causing movement of thefirst disc on the hub to bring the other pad associated with that discinto contact with the first disc. The movement continues moving the padswhich are between the discs so that one of them contacts the second discwhich moves into contact with the other pad associated with the seconddisc which is the pad which is fixed relative to the hub. The guidancemember is supported by bolts which pass therethough and fix it to saidcylinder. As further explained in WO 98/26191, the bolts enable thebending and shearing forces applied to the pads during operation of thebrake to be taken by the bolts while the guidance member itself can bemade from lower strength material. The slideway is relatively complex toassemble and requires relatively long holes to be drilled through theguidance member to receive said bolts.

It is an object of the present invention to provide a disc brake havinga simplified slideway which is easier to assemble.

SUMMARY OF THE INVENTION

The invention provides a disc brake comprising a disc, friction materialpads arranged on opposite sides of the disc, and an operating mechanismoperable to bring the pads into contact with the disc so that the padsapply a braking force to the disc, the brake also comprising a slidewayon which at least one of said pads is supported for sliding movementtowards or away from the disc, characterised in that said slideway isformed by a guidance member which defines at least two parallel groovesin a surface of the guidance member, the grooves extending parallel tothe direction of the slideway, the guidance member being supported byparallel rods which are received in said grooves.

In a disc brake according to the invention, the grooves in the guidancemember are much easier to form than long holes through the guidancemember and, in assembling the brake, the guidance member can simply befitted over the rods.

A disc brake according to the invention may be of the type disclosed inWO 98/25804. That brake comprises two discs which are slidable on thesame hub under the control of leaf springs which act between the hub andthe discs. The brake also comprises a cylinder which is integrallyformed with a suspension link and a caliper also fixed to the suspensionlink, the caliper having supports for friction material pads mountedthereon.

Preferably, in a disc brake according to the invention said guidancemember defines a protuberance between said grooves, the protuberancebeing a close fit between two of the rods.

The rods are, preferably, provided by bolts.

The guidance member may be made of plastics material or metal such asaluminium. Preferably, the guidance member is formed as an extrusion,since the guidance member can be formed with a constant transversecross-sectional shape.

THE DRAWINGS

There now follows a detailed description, to be read with reference tothe accompanying drawings, of a disc brake which is illustrative of theinvention.

In the drawings.

FIG. 1 is a vertical cross-sectional view taken through the illustrativedisc brake; and

FIG. 2 is a perspective view on an increased scale of a guidance memberof a caliper of the illustrative disc brake.

DETAILED DESCRIPTION

The illustrative disc brake 10 shown in FIG. 1 is for a wheel (notshown) of a car. The brake 10 comprises a disc 12, a further disc 14,and a hub 16, on which the wheel can be mounted. The discs 12 and 14 andthe hub 16 are arranged to rotate about a common central axis 18.

The hub 16 comprises an internally splined hollow inner cylindricalportion 16 a which is arranged to receive a drive shaft (not shown)which drives the wheel. The hub 16 also comprises an external flange 16b at one end of the portion 16 a. This flange 16 b has bolt holes (notshown) through which the wheel can be bolted to the flange 16 b in aconventional manner. The flange 16 b also serves to connect the portion16 a to an outer hollow cylindrical portion 16 d of the hub 16.

The two discs 12 and 14 are mounted on the cylindrical outer surface ofthe hub portion 16 d so that the hub 16 and the two discs 12 and 14rotate as a unit about the axis 18 and the discs 12 and 14 can performaxial sliding movement on said hub 16. Specifically, four grooves 20 areformed in the outer cylindrical surface of the portion 16 d of the hub16 and four teeth 22 which project inwardly from each of the discs 12and 14. The teeth 22 enter the grooves 20 and are a sliding fit therein.

The brake 10 also comprises four friction material pads 26 which arearranged with two of the pads 26 on opposite sides of each of the discs12 and 14. The pads 26 are for braking the discs 12 and 14 by engagingside surfaces of the discs. The friction pads 26 are secured to threebacking plates 28, one backing plate 28 a being between the discs 12 and14 and the others being on opposite sides of the discs 12 and 14 to theplate 28 a. The median plate 28 a has friction material pads 26 securedto both of its faces. When the brake is applied, a movable outerfriction material pad 26 is moved until the four pads 26 and the discs12 and 14 are all in contact with one another, the discs 12 and 14 andthe plate 28 a sliding axially to accommodate this movement.

The brake 10 also comprises resilient means in the form of four leafsprings 32 mounted on the hub 16 and engaging the discs 12 and 14 sothat the springs 32 apply force radially between each of the discs 12and 14 and the hub 16. The leaf springs 32 are equally distributedcircumferentially around the hub 16, each being mounted on one of thebottom surfaces of the grooves 20, ie each spring 32 is mounted in oneof the grooves 20 and acts between the bottom surface of the groove andan inner surface of the teeth 22 which enter the groove 20.

The illustrative brake 10 also comprises an operating mechanism operableto bring the pads 26 into contact with the discs 12 and 14. Theoperating mechanism is in the form of a piston and cylinder assemblycomprising a piston 50 and a cylinder 52, the cylinder 52 is fixedrelative to the axis 18 being integral with a suspension link (notshown) of the vehicle as disclosed in WO 98/25804. The assembly 50, 52is operable to move a first of the pads 26 into contact with the disc 12and to cause relative movement between the assembly 50, 52 and the disc12 to bring the other pad 26 associated with the disc 12 into contactwith the disc 12, so that the pads 26 apply a braking force to the disc12. Specifically, a caliper 54 is mounted on the cylinder 52 and bridgesthe edges of both discs 12 and 14. The furthest pad 26 from the cylinder52 has its support plate 28 fixedly mounted on the caliper 54 while thesupport plates 28 of the remaining pads 26 are slidable on the caliper54. When the piston 50 is moved outwardly from the cylinder 52 byhydraulic fluid under pressure, it directly presses the support plate 28of the nearest pad 26 so that the plate 28 slides on the caliper 54. Thenearest pad 26 presses the disc 12 so that it slides on the hub 16. Thedisc 12, in turn, presses on the pad 28 on the opposite side thereofcausing the support plate 28 a to slide on the caliper 54. The movementof the plate 28 a causes the pad 26 on the plate 28 a which faces thedisc 14 to contact the disc 14. The disc 14 slides on the hub 16 untilit contacts the pad 26 on the plate 28 which is fixed to the caliper 54.The brake 10 is now “on” with the discs 12 and 14 both engaged on bothsides by one of the pads 26.

The caliper 54 comprises two rods 70 (FIG. 2) which extend parallel toone another axially of the hub 16. The rods 70 are provided by boltswhich pass through holes (not shown) in the plate 28 which supports thepad 26 which is furthest from the cylinder 54. The bolts are alsoreceived in tapped holes (not shown) in the cylinder 52. Bolts of thistype are disclosed in WO 98/26191. The bolts may also be arranged toextend in the opposite direction, ie the bolts pass through holes in thecylinder 52 and are received in tapped holes in the furthest plate 28.The caliper 54 also comprises a guidance member 72 which forms aslideway of the brake 10 on which the movable pads 26 are supported forsliding movement towards or away from the discs 12 and 14. Specifically,the guidance member 72 comprises oppositely-facing arcuate side surfaces72 a on which hook-like projections of the support plates 28 of themovable pads 26 are slidable.

The guidance member 72 also defines two parallel grooves 72 b in a lowersurface 72 c thereof. The.grooves 72 b extend parallel to the directionof the slideway defined by the surfaces 72 a and are arranged to be aclose fit over the rods 70. The guidance member 72 is supported by therods 70 which are received in said grooves 72 b and is held in positionbetween the fixed plate 28 and the cylinder 52 by clamping force appliedby the bolts 70 which form the rods.

The guidance member 72 also comprises a protuberance 72 d between saidgrooves 72 b, the protuberance 72 d being a close fit between said rods70.

The guidance member 72 has a constant transverse cross-sectional shapeand is formed of aluminium as an extrusion, although other materials,including plastics materials such as glass fibre re-inforced phenolicresin, could be used.

The guidance member 72 is easily assembled on the rods by fitting thegrooves 72 b over the rods 70.

What is claimed is:
 1. A disc brake comprising a disc, friction materialpads arranged on opposite sides of the disc, and an operating mechanismoperable to bring the pads into contact with the disc so that the padsapply a braking force to the disc, the brake also comprising a slidewayon which at least one of said pads is supported for sliding movementtowards or away from the disc, wherein said slideway is formed by aguidance member which bridges the edge of the disc and defines at leasttwo parallel grooves in a surface of the guidance member which faces theedge of the disc, the grooves extending parallel to the direction of theslideway, the guidance member being supported by parallel rods which arereceived in said grooves.
 2. A disc brake according to claim 1, whereinsaid guidance member defines a protuberance between said grooves, theprotuberance being a close fit between two of the rods.
 3. A disc brakeaccording to claim 1, wherein said rods are provided by bolts.
 4. A discbrake according to claim 1, wherein the guidance member is made ofplastics material.
 5. A disc brake according to claim 1, wherein theguidance member is formed as an extrusion.